They look pretty good. Just a few notes:

1. Looks like everything is one flat color. You should work on layering colors and using inks to shade.
2. Plain black guns look lazy. Hit the bolters with thinned gunmetal and then paint the casing over black again.
3. Two-toned helmets rarely look good. Seems like you did a clean job, but the colors look too flat and thick.
4. Do none of these guys have backpacks? That's kind of the power source to their armor, and the armor looks wonky without it.

The Dark Angels Colors are pretty much 1 color anyways, I went beyond by added a second color of green to it. Some of the bolters are missing the highlights as you stated, the only one with the a backpack is the Plasma Cannon. Backpacks and Shoulder Pads are usually the last thing I put on the mini's, they will be put on shortly.

Okay, so you ARE putting packs on. Also, about the one color thing, I meant layers of color. Usually you want to work up colors in at least 3 layers: starting with a something dark, building up to the color you want, and finally highlighting with a shade brighter.

Yes the backpacks will be put on, probably going to have trouble with the two that have the should wings on them we'll see.